In underwater communication systems, cables are typically laid in water in order to connect a first terminal station to a second terminal station. In such systems a cable may be used for conveying significant amount of data between the two terminal stations while delivering power to the submerged amplifiers from the terminal stations. Such cables are typically referred to as trunk cables or simply trunk.
In submarine optical telecommunication systems there are circumstances where it may be needed to connect several land stations or offshore platforms to the trunk. Typically, this is done by using additional segments of cable in order to connect a land station to the trunk. The cable segment is typically connected to the trunk by means of a branching unit.